An Xfinity sales consultant, left, explains Xfinity's new mobile service to a customer on June 26, 2017, at Xfinity's location in Chicago’s Lakeview neighborhood. Comcast is offering Xfinity Mobile only to its internet customers.

An Xfinity sales consultant, left, explains Xfinity's new mobile service to a customer on June 26, 2017, at Xfinity's location in Chicago’s Lakeview neighborhood. Comcast is offering Xfinity Mobile only to its internet customers. (Alexandra Wimley/Chicago Tribune)

The biggest hang-up: You need to be an existing Xfinity internet customer to get the wireless service. Xfinity has about 25 million internet subscribers and a total customer base of 29 million, all of whom will be targets for the new mobile offering, said Randall Hounsell, vice president of product and marketing for Xfinity Mobile.

Traditional pay-TV providers are projected to lose nearly 11 million subscribers nationwide by 2021, falling to about 82 million households, according to a report issued Monday by research firm Kagan. Meanwhile, nascent streaming services such as Sling TV, DirecTV Now and PlayStation Vue are projected to reach 11 million households by 2021.

While the subscription bundle has an appeal for consumers, the search for alternatives to traditional pay-TV providers continues to accelerate, said Ian Olgeirson, research director for Kagan, part of S&P Global Market Intelligence.

"We don't see anything that indicates that is going to slow down anytime soon," Olgeirson said.

Adding wireless phone service to its existing offerings, which include internet, home phone, home security and television, may be one way for Comcast to stem the tide.

Plans include an introductory monthly rate of $45 per line up to five lines for unlimited data, a two-year rate guarantee and no contract. The monthly rate goes up to $65 per line beginning in August.

Olgeirson said Comcast faces stiff competition in the wireless market.

"I think that it will be well-received by its customers, but there's nothing that sets the wireless component apart from every other service that's being offered," he said. "But I do think they will look for ways to differentiate down the road."

Rival AT&T has been offering wireless for years, but it is essentially unbundled from its pay-TV, home phone and internet products.

AT&T basic unlimited wireless service is $60 per month for the first line, with a $25 monthly discount available for DirecTV Now, its streaming video service.

Chicago is among the first markets in the country to roll out Xfinity Mobile retail outlets. The inaugural locations are in Crystal Lake, Orland Park, Oak Brook, Vernon Hills, Merrillville, Ind., and Chicago's Lakeview neighborhood, with additional stores expected to open over the next few weeks.

Comcast launched Xfinity Mobile online in May, with the first retail outlets opening last week in the Philadelphia area.